The present invention relates to a variable displacement type swash plate compressor.
Japanese Unexamined Patent Application Publication No. 2014-190265 discloses a conventional variable displacement type swash plate compressor (hereinafter simply referred to as compressor). The compressor includes a housing, a drive shaft, a swash plate, a link mechanism and a plurality of pistons. The housing has therein a swash plate chamber and a plurality of cylinder bores. The drive shaft is rotatably supported in the housing. The swash plate is mounted on the drive shaft for rotation therewith in the swash plate chamber. The link mechanism is provided between the drive shaft and the swash plate and permits changing of an inclination angle of the swash plate relative to a direction perpendicular to the axis of rotation of the drive shaft. Each piston is received in its corresponding cylinder bore and reciprocally movable in the cylinder bore with a stroke length that is determined by the inclination angle of the swash plate thereby to form a compression chamber in the cylinder bore.
The compressor further includes a partitioning body, a movable body, a control chamber, and a control mechanism. The partitioning body and the movable body are disposed in the swash plate chamber and mounted on the drive shaft for rotation therewith. The movable body is movable relative to the partitioning body in the axial direction of the drive shaft so as to change the inclination angle of the swash plate. The control chamber is defined between the partitioning body and the movable body and causes the movable body to be moved with its internal pressure. The control mechanism controls the pressure in the control chamber.
The movable body is connected to the swash plate through the link mechanism. Specifically, the link mechanism includes a first arm and a second arm that are provided in the movable body, and a traction portion that is formed in the swash plate. The first and second arms extend toward the swash plate, and the traction portion projects toward the movable body in a space between the first and second arms.
The first arm has therethrough a circular first hole and the second arm has a circular second hole, respectively. The traction portion includes a pin having one end thereof inserted through the first hole and the other end thereof through the second hole, respectively.
The movement of the movable body away from the swash plate in the axial direction of the drive shaft by an increased pressure in the control chamber is transmitted through the first and second holes of the first and second arms and the link pin held by the traction portion. As a result, the movable body pulls the swash plate thereby to increase the inclination angle of the swash plate.
According to the compressor disclosed in the Publication, the relative positional relation between the link pin and the first and second holes remains constant without being affected by the change of the inclination angle of the swash plate. In order to enhance the freedom of setting the pattern of changing of the inclination angle of the swash plate, it may be contemplated, for example, to form the first and second holes into elongated holes and to form a first guide surface that is contactable with the link pin on a side thereof opposite to the swash plate and a second guide surface that is contactable with the link pin on the side thereof opposite to the swash plate so that the link pin is disposed slidably and reciprocally on the first and second guide surfaces with the change of the inclination angle of the swash plate.
However, it is difficult for a compressor having such configuration to achieve both the efficient conversion of pulling force of the movable body into the change of the inclination angle of the swash plate and the enhancement of the smooth operation and the wear resistance of the movable body that rotates with the drive shaft.
In order for the movable body to change the inclination angle of the swash plate with a small force, it is preferable that the link pin on which the pulling force of the movable body acts should be spaced at a distance from the axis of rotation of the drive shaft. However, such position of the link pin involves an increase in the dimension of the first and second arms as measured in a direction separating from the axis of rotation and, therefore, the weight of the respective first and second arms tends to be increased locally at positions that are distant from the axis of rotation. As a result, the center of gravity of the movable body is shifted away from the axis of rotation and, therefore, the centrifugal force that acts on the movable body is increased to cause an irregular movement of the movable body, which hinders the enhancement of the smooth operation and the wear resistance of the movable body.
Meanwhile, in order to reduce the centrifugal force that acts on the movable body, the center of gravity of the movable body should preferably be located as close to the axis of rotation as possible. In this case, the link pin tends to be disposed close to the axis of rotation so as to reduce the weight of the first and second arms. As a result, a greater force may be required for the movable body to change the inclination angle of the swash plate, and the pulling force of the movable body may not be efficiently converted into the change of the inclination angle of the swash plate.
The present invention, which has been made in view of the above circumstances is directed to providing a variable displacement type swash plate compressor that achieves both the efficient conversion of the pulling force of the movable body into the change of the inclination angle of the swash plate and the enhancement of the smooth operation and the wear resistance of the movable body that rotates with the drive shaft.